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Direct-effect radiation chemistry of solid-state carbohydrates using EMR and DFT

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HPC-UGent: the central High Performance Computing infrastructure of Ghent University
Abstract
To contribute to a mechanistic understanding of radical reaction pathways in the sugar-phosphate backbone of DNA, we are investigating primary radicals induced by X-rays, as well as their transformation into stable radicals or diamagnetic products, in crystalline sugar and sugar derivatives. Radicals are identified and characterized mainly via the hyperfine interactions of the electron spin with protons in the molecular environment. These interactions are determined experimentally with electron magnetic resonance (EMR) techniques and compared to theoretical ab initio calculations based on density functional theory in a periodic approach. Different stages of the radiation-induced processes are investigated by irradiating in situ at various temperatures and controlled annealing experiments. Here, results obtained in single crystals of the dipotassium salt of glucose 1-phosphate (K2G1P) and the disaccharides sucrose and trehalose are presented. The dominant radical in K2G1P after irradiation at 77 K exhibits a broken phospho-ester bond and is chemically identical to one of the major stable sucrose radicals, the latter all being characterized by a broken glycosidic bond. This suggests that the ester bond is radiation sensitive and that the phosphate group is not essential for the reaction pathway leading to this scission. Surprisingly, however, no evidence for glycosidic bond scission has so far been observed in trehalose. Rather, a simple H-abstraction alkyl radical is remarkably stable in this system. In all three compounds, dominant radicals are formed with one or several concerted carbonyl group formations. Extended studies are necessary to establish how and to which extent structural or geometrical factors determine the radiation chemistry, but certain general principles are starting to emerge.

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Chicago
De Cooman, Hendrik, Mihaela Adeluta Tarpan, Ewald Pauwels, Henk Vrielinck, E Sagstuen, Michel Waroquier, and Freddy Callens. 2010. “Direct-effect Radiation Chemistry of Solid-state Carbohydrates Using EMR and DFT.” In Radiation Damage to DNA, 11th International Workshop, Abstracts.
APA
De Cooman, H., Tarpan, M. A., Pauwels, E., Vrielinck, H., Sagstuen, E., Waroquier, M., & Callens, F. (2010). Direct-effect radiation chemistry of solid-state carbohydrates using EMR and DFT. Radiation Damage to DNA, 11th International workshop, Abstracts. Presented at the 11th International workshop on Radiation Damage to DNA.
Vancouver
1.
De Cooman H, Tarpan MA, Pauwels E, Vrielinck H, Sagstuen E, Waroquier M, et al. Direct-effect radiation chemistry of solid-state carbohydrates using EMR and DFT. Radiation Damage to DNA, 11th International workshop, Abstracts. 2010.
MLA
De Cooman, Hendrik, Mihaela Adeluta Tarpan, Ewald Pauwels, et al. “Direct-effect Radiation Chemistry of Solid-state Carbohydrates Using EMR and DFT.” Radiation Damage to DNA, 11th International Workshop, Abstracts. 2010. Print.
@inproceedings{976448,
  abstract     = {To contribute to a mechanistic understanding of radical reaction pathways in the sugar-phosphate backbone of DNA, we are investigating primary radicals induced by X-rays, as well as their transformation into stable radicals or diamagnetic products, in crystalline sugar and sugar derivatives. Radicals are identified and characterized mainly via the hyperfine interactions of the electron spin with protons in the molecular environment. These interactions are determined experimentally with electron magnetic resonance (EMR) techniques and compared to theoretical ab initio calculations based on density functional theory in a periodic approach. Different stages of the radiation-induced processes are investigated by irradiating in situ at various temperatures and controlled annealing experiments.
Here, results obtained in single crystals of the dipotassium salt of glucose 1-phosphate (K2G1P) and the disaccharides sucrose and trehalose are presented. The dominant radical in K2G1P after irradiation at 77 K exhibits a broken phospho-ester bond and is chemically identical to one of the major stable sucrose radicals, the latter all being characterized by a broken glycosidic bond. This suggests that the ester bond is radiation sensitive and that the phosphate group is not essential for the reaction pathway leading to this scission. Surprisingly, however, no evidence for glycosidic bond scission has so far been observed in trehalose. Rather, a simple H-abstraction alkyl radical is remarkably stable in this system. In all three compounds, dominant radicals are formed with one or several concerted carbonyl group formations. Extended studies are necessary to establish how and to which extent structural or geometrical factors determine the radiation chemistry, but certain general principles are starting to emerge.},
  author       = {De Cooman, Hendrik and Tarpan, Mihaela Adeluta and Pauwels, Ewald and Vrielinck, Henk and Sagstuen, E and Waroquier, Michel and Callens, Freddy},
  booktitle    = {Radiation Damage to DNA, 11th International workshop, Abstracts},
  language     = {eng},
  location     = {Atlanta, GA, USA},
  pages        = {1},
  title        = {Direct-effect radiation chemistry of solid-state carbohydrates using EMR and DFT},
  year         = {2010},
}